Allergy never ceases to surprise and amaze me for the multiplicity of symptoms that it can cause. It is now clear to me that any part of the body can react allergically. Irritable bowel syndrome is partly due to allergy in the gut, migraine is allergy in the brain, asthma is allergy in the lungs, so why not allergic muscles? The more I look for this condition the more I find it, and it is obvious when you look for it!
The allergy cycle
The natural progression of allergy is for allergens to start producing symptoms in one target organ and move on to another. So the typical history through life of the dairy allergic person would be to start with colic as a baby, then move on to other manifestations such as toddler diarrhoea, catarrh, ear infections and sore throats, irritable bowel syndrome, migraine, arthritis, fatigue and allergic muscles!
How do allergic muscles start? What seems to happen is that muscles get sensitised as a result of mechanical damage. Tearing or bruising the muscle means that it comes in direct contact with blood, which may be carrying food antigens. I suspect the allergy is switched on at that time and the pain which follows the muscle damage and which persists long term is mis-attributed to damage, when actually it is sensitisation. So a torn muscle in the back from, say, lifting a heavy load could sensitise to, say, dairy products and it is the consumption of dairy subsequently which keeps the problem on the boil.
The clinical picture
The diagnosis is made more difficult because we often see delayed reactions, which start 24 or 48 hours after allergen exposure and last for several days. Muscles can only react in one way, which is with contraction and this can vary from a low grade cramp to muscle tics or jumping, to acute lancinating pain. I suspect the type of reaction depends on how much of the food is being consumed - regular consumption results in chronic low grade spasm and cramp, but the odd inadvertent exposure in somebody who is normally avoiding that food can cause acute lancinating pain so severe that the sufferer literally collapses. Typically this just lasts a few seconds. Pain is triggered by stretching the affected muscle. Initially any stretch will cause it; then, as things settle down, only a sudden stretch will cause it. The sufferer protects himself from the pain by moving slowly. Other muscles in the vicinity of the allergic muscles may also go into spasm to protect against sudden inadvertent stretching and this causes a more generalised muscle spasm and stiffness. Because muscles can only react in one way, through contraction, this produces symptoms such as cramp, restless legs, jerking muscles, twitching muscles, fasciculation, and some of these muscle contractions will be accompanied by pain. There is further complication because if muscles contract inappropriately they can damage themselves literally by pulling themselves apart (and, indeed, this is the mechanism that athletes employ to get fitter - if you damage the muscles slightly, this stimulates the production of more muscle). Further pain develops because the blood circulation through muscle is disturbed and there is the build up of toxic metabolites, in particular lactic acid. Lactic acid causes pain. So often we then see a particular vicious cycle with allergic muscles causing spasm, spasm causing build up of toxic metabolites, which causes more pain and the muscles react to pain with further spasm.
Muscle pain is one of the greatest pains that one can experience. Indeed, labour pains are, of course, muscle pains. Biliary colic and renal colic are also muscle pains - ask any sufferer how bad the pain is!
Typically the problem is much worse in the morning and improves as the day progresses. Often there are good days and bad days. Gentle regular exercise, such as walking, is very helpful and indeed some patients find that they have to exercise very intensely and very regularly to keep the problem at bay (if the allergen has not been recognised). Heat, hot bath, gentle massage help to relax the muscle in the short term, as does keeping the body in one particular position, but the first movement after these interventions has to be done carefully or the pain will come straight back again. Diazepam affords some relief because I suspect it makes the irritable, allergic muscle less twitchy.
I have two patients with "stiff man syndrome" who have been much improved by identifying and desensitising to allergens. My guess is stiff man syndrome is an extreme version of allergic muscles.
Investigations, including MRI scans and x-rays, are normal. However, allergic muscles can obviously co-exist with other pathology, such as arthritis and osteoporosis, and may be mis-attributed to these factors.
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